How do i use FFMPEG to convert mp4 to a single file encrypted hls?

Question

I have a simple mp4 video that i want to convert to hls 4 encrypted single file stream how can i do that using ffmpeg ?

i have already tried this command

ffmpeg -i bigbuckbunny.mp4 -hls_time 20 -hls_flags single_file -hls_key_info_file key_info out.m3u8

and the output stream keeps repeating after reaching a certain point (it never reaches the end of the video)